Implement local langevin thermostat

[J-Hizzle]

Solves #45

[J-Hizzle]

This should also be implemented for the velocityVerletLangevinThermostat module.

[XzzX]

This should also be implemented for the velocityVerletLangevinThermostat module.

We can do this once this is resolved in a separate PR.

[Copilot]

Pull Request Overview

This PR implements a local Langevin thermostat by adding an apply_if method that accepts a predicate to selectively apply the thermostat to specific atoms. The implementation follows existing patterns in the codebase (e.g., ThermodynamicForce).

• Refactors the existing apply method to call apply_if with a predicate that always returns true
• Adds template method apply_if that accepts a predicate determining which atoms to thermostat
• Includes comprehensive unit and integration tests for the new functionality

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
mrmd/action/LangevinThermostat.hpp	Adds template apply_if method with predicate support using C++20 concepts, includes <concepts> header
mrmd/action/LangevinThermostat.cpp	Refactors apply to delegate to apply_if with always-true lambda predicate
mrmd/action/LangevinThermostat.test.cpp	Adds Local test case verifying selective thermostat application using IsInSymmetricSlab predicate
tests/LangevinThermostat/LangevinThermostat.cpp	Adds LocalLangevinThermostat integration test, includes whitespace cleanup in copyright header

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